#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	float month = 0, average = 0, sum = 0;
	int i = 0;
	for (i = 0; i < 12; i++)
	{
		scanf("%f", &month);
		sum += month;
	}
	average = sum / 12;
	printf("$%.2f", average);
	return 0;
}